CKD-EPI Cystatin C (2012)

Adult2012Recommended

Race-free cystatin C equation — current KDIGO-recommended cystatin C equation (unchanged in the 2021 publication)

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Calculate CKD-EPI CysC

Enter the values required by this equation to estimate the result.

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For educational and clinical reference use. Interpret results in clinical context.

Formula

eGFR=133×min⁡(SCys0.8,1)−0.499×max⁡(SCys0.8,1)−1.328×0.9962age×0.932[F]\text{eGFR} = 133 \times \min(\frac{\text{SCys}}{0.8}, 1)^{-0.499} \times \max(\frac{\text{SCys}}{0.8}, 1)^{-1.328} \times 0.9962^{\text{age}} \times 0.932^{[F]}

Formula constants

SymbolDescriptionValue
133Base coefficient
0.8Cystatin C reference valuemg/L
−0.499Exponent when SCys/0.8 < 1
−1.328Exponent when SCys/0.8 ≥ 1
0.9962Age decay factor — full-precision coefficient from Inker 2021 Table 2 (printed as 0.996 in the 2012 paper)per year
Sex factorSex-dependent multiplier
Female:0.932
Male:1.000
SCysinputSerum cystatin Cmg/L
AgeinputPatient ageyears

Required inputs

AgeSexCystatin C

Validated age range

18 to 120 years

Limitations

  • Requires standardized cystatin C assay (ERM-DA471/IFCC)
  • More expensive than creatinine
  • Limited availability in some settings
  • Cystatin C affected by thyroid dysfunction, corticosteroids, and inflammation

Clinical notes

  • Current KDIGO-recommended cystatin C equation
  • Never included a race term; carried over unchanged into the 2021 CKD-EPI publication
  • Recommended for confirmatory testing
  • Less affected by muscle mass than creatinine
  • Requires cystatin C standardized to ERM-DA471/IFCC

References

  • [1]Inker LA, Schmid CH, Tighiouart H, et al. Estimating glomerular filtration rate from serum creatinine and cystatin C. N Engl J Med. 2012;367(1):20-29. doi:10.1056/NEJMoa1114248
  • [2]Inker LA, Eneanya ND, Coresh J, et al. New creatinine- and cystatin C-based equations to estimate GFR without race. N Engl J Med. 2021;385(19):1737-1749. doi:10.1056/NEJMoa2102953
  • [3]KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int. 2024;105(4S):S117-S314. doi:10.1016/j.kint.2023.10.018

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